The conversion of crude oil into the various products desired in the marketplace generally involves a series of process steps. Typically, distillation of the crude oil is followed by further processing for the purpose of producing gasoline, kerosene, jet fuel, and other fuels. Examples of some such processes include those generally referred to as hydroprocessing which includes those known as hydrocracking, ultracracking, hydroconversion, hydrorefining, reforming, and hydrodesulfurization and in general any process in which hydrogen is produced or consumed. Under the reaction conditions employed in such processes the bed of catalyst tends, over time, to become fouled with a layer of carbon and/or inorganic deposits, especially when the feedstock includes the heavier, more refractory fractions of the crude oil. The accumulation of such deposits tends to reduce the flow of the feedstock through the catalyst bed. It is often observed that the deposits cause such a restriction that, even though the catalyst is still active, it becomes difficult to introduce the feedstock into the reactor. The reaction then becomes pressure limited and thus even though the catalyst is still active, less hydrocarbon can be processed. If the restriction of flow becomes too great it can actually cause the catalyst bed to collapse, effectively stopping the process. Prior to such time, the process can be interrupted and at least the deposit fouled inlet portion of the catalyst bed can be removed and replaced.
The present invention provides a method for increasing the time that a catalyst can be employed effectively without having to interrupt the process.
The present invention also provides a process which will inhibit and suppress fouling of the catalyst bed by deposits.
Surprisingly, the present invention is also useful for reversing the flow restricting effects of deposits already existing on a previously used catalyst.
The present invention also provides a method of reducing the fouling of the catalyst bed by deposits without adversely affecting the catalytic properties of the catalyst to any significant degree.
The only process of which the present inventors are aware which claims to provide similar results is the process disclosed in U.S. Pat. No. 4,024,048, the disclosure of which is incorporated herein by reference. The process of that patent employs a treating agent comprising phosphite or phosphate esters. The treating agent employed in the present invention differs in that it does not require the presence of phosphite or phosphate esters.